There presently exist numerous tamper indicating closures for containers, bottles, etc. These closures come in various materials for example, metals and plastics predominently. Metal however has the disadvantage of being expensive, and prone to leaving sharp edges. In addition experience has proven that the tamper proof evidence in the form of a detachable ring many times will not remain on the neck of the bottle.
The closure may be adapted to allow for a portion thereof to be left on the container after opening as an indicator of tampering. This is often accomplished by requiring the user to pull a tear portion or strip from the closure typically situated between the threads of the closure and the portion remaining on the container to allow the unscrewing of the closure. This requires two operations for removal of the closure in addition to necessitating a discarding of the tear strip.
Other types of closures provide for a breakaway portion which breaks from the closure during unscrewing thereby providing for a single operation, eliminating the tear strip. This type of closure comes in various forms, single piece or ones having a plurality of pieces. In the latter situation, the more pieces involved, the greater the cost in fabrication and assembly, thereby limiting their application.
In providing for a tamper proof closure for liquor or spirit containing bottles, it is desirable to provide a linerless one piece closure having straight side walls which assures that the tamper proof evidence remain on the bottle neck whose neck finish is of simple design and does not possess a stepped configuration.
There presently exists few, if any, single piece straight side wall type closures that do not involve the actual molding of the piece or other work on the closure such as a heat shrinking technique after it is placed on the container, to provide for tamper indication. A straight side closure has been proposed of multiple part construction with the attendant disadvantages noted in the above.
Usually stepped or offset closures are utilized since they facilitate their molding in such a manner to get the closure off the core, but even these usually involve complicated molding techniques and structures, aside from any asthetic considerations. Furthermore, the neck finishes are stepped which in the case of glass bottles add to the complexity of the product.
A further consideration in closure design is the material from which it is molded and the molding technique employed. In the case of polyethylene closures, they are usually made by a strip molding procedure. Since the threads of the closure are made of the same material, even if a tight threading with the container was used, the closure could stretch allowing it to "back-off" causing leaks. This is especially true if the container is made of a relatively dense material such as glass. To prevent leaks, it is usually necessary that a sealer or liner between the crown of the closure and the container be provided, adding to the cost of the device.
Further, even if one was to attempt to use the break off portion as a means of preventing "back-off", once this portion is broken, the closure would be incapable of providing an effective resealing of the container.